Thanks for yor quick response,
Ok, I see it is necessary. But does ++i means increment in ones?

When we did for loops in vb.net, I remember doing something like:
var i as integer
for i = 0 to 10 step one

step one meant to increment by ones. I asked my instructor he said if I had step 2, it will increment in two (ie possibly half of the total number of steps if I had step 2). I have no idea why would someone increment in two or more steps. Why not makes the steps lesser instead. So step one in vb.net = i++ j/script?

JavaScript is very strong language, if any one is really interested in website development, then he has to learn JavaScript properly, though it is not complete language, but very useful in web development.